Magnetostatic relay



ited States Patent Ofiice W533i Patented Apr. 9, 1963 3,085,234 MAGNETOSTATEQ RELAY Claude Monin, Viiiennes-sur-Seine, France, assignor to Qompagnie Industrielle ties Telephones, Paris, France,

a French corporation Filed May 25, $59, Ser. No. 815,677 Claims priority, application France June 2, 1958 8 Claims. (Cl. 348-174) The present invention concerns control and storage devices which are suitable more especially for use in automatic telephony and remote control.

There is already disclosed in the parent US. Patent 2,946,896, assigned to the assignee of the present application, a magnetostatic relay comprising a transistor connected to the output of a magnetic amplifier and permitting of obtaining an output direct-current capable of assuming two well-defined values as a function or the control ampere-turns.

in the circuit arrangement according to the said parent patent, the output of the magnetic amplifier is a common point which is connected on the one hand to the emitter of a transistor and on the other hand to a resistance. When the output current reaches a predetermined value, the transistor becomes conductive, but with this arrangement no benefit is derived from the increase in current which is obtained from the transistor, because the current of the emitter is slightly higher than the current of the collector. The present invention relates to a magnetostatic relay which is not attended by the aforesaid disadvantage. The relay according to the invention is characterised in that the output terminal of the magnetic amplifier is connected to a point which is in turn connected on the one hand to the base of a transistor and on othe other hand to ground through a resistance, the emitter of the transistor being connected to a negative potential. Under these conditions, when the potential of the output terminal of the magnetic amplifier is sufiiciently negative, the transistor becomes conductive, but the current in the base is very much lower than the current of the collector, and a current gain is thus obtained. It is also possible further to limit the current in the base of the transistor by means of a resistance inserted between the output terminal of the magnetic amplifier and the base of the transistor.

Further features and advantages of the invention will become apparent from the description thereof which is given in the following with reference to the figures of the accompanying drawings, which show by way of example two possible constructional forms of a relay according to the invention.

FIGURE 1 is the circuit diagram of a relay according to the invention.

FIGURE 2 is a variant of FIGURE 1.

FIGURES 3 to 8 are curves relating to the operation of the device according to FIGURE 1.

The relay illustrated in FIGURE 1 comprises a saturable magnetic core s on which are wound a number of windings a, b, c and d. The winding a, which is connected in series with a rectifier R is fed from an alternating-current source AB, the rectifier R being oriented in a direction such that it allows only the negative halfcycles to pass. The windings b, c and d carry direct currents, the winding b being a control winding, the winding c a bias winding and the winding d a feedback winding. In any case, the algebraic sum of the ampere-turns of the windings b, c and d will be broadly referred to as the control ampere-turns.

The winding (1 is connected through the rectifier R to a point D which is connected, on the one hand, to the base ba of a transistor T and on the other hand to ground through a resistance R The emitter e of the transistor T is directly connected to the negative pole of a directvoltage source U When the connection NQ is established, the collector C0 of the said transistor is connected through a load resistance R to the negative pole of a direct-voltage source U U being distinctly greater, in absolute value, than U (for example U =48 volts and U =1.5 volts). Connected to the point F of the collector is one electrode of a condenser C of which the other electrode is grounded. It is possible to connect the feedback winding d into the output circuit of the relay by breaking the connection NQ and establishing connections MN and PQ.

The circuit arrangement according to FIGURE 2 differs from that of FIGURE 1 only in two respects: on the one hand, a resistance R has been introduced between the output terminal of the magnetic amplifier and the base of the transistor to reduce the current in the base; the current corresponding to the emitter being much higher, the resistance R being so chosen as to obtain across the load resistance the desired current which, as is known, will be slightly lower than that across the emitter. On the other hand, there has been introduced between the point F and the collector a resistance R the function of which will hereinafter be described.

FIGURE 3 illustrates the curve G of the output current 1 of the magnetic amplifier through the winding a and the rectifier R as a function of the control ampereturns due to the windings b and c.

The transistor illustrated in FIGURE 1 being assumed to be of the p-n-p-junction type, its emitter e must be positive in relation to the base in order that it may be conductive. Now, since the emitter is here connected to a negative pole and the rectifier R transmits only the negative halt-cycles, it is necessary to have U,, -R I or I being the minimum output current of the magnetic amplifier above which the transistor is conductive. It therefore constitutes a threshold current.

FIGURE 4 shows on the one hand the curve G of FIGURE 3 and on the other hand the curve G of the threshold current 1 which is obviously constant for a given circuit arrangement. It intersects the curve G at two points S and S which correspond to control ampereturns (N IQ and (N TJ respectively. The values of the current T which render the transistor conductive are therefore located above the curve G of 1 These values are represented by the curve G of FIGURE 5.

The current across the collector follows substantially the variation of the current across the emitter as long as the voltage of the collector remains lower than that of the base. Beyond this limit, the current is stabilised exactly at a value such that the voltages of the base and of the collector are equal.

This value is therefore such that I U base potential 1 e RD The curve 6.; of FIGURE 6 represents the current I =I across the load resistance R It will be noted that at ampere-turn values N l higher than (N IQ the output current suddenly changes from a zero value to the constant value I The potential of the point F (see FIG- URE 2), which is that of one electrode of the condenser C thus suddenly changes from the value U to a value close to zero. The condenser C discharges for the greater part across the transistor T. The resistance R is a protective resistance which limits the strength of the discharge current of the condenser. A similar reasoning would be valid at the instant when the output current I becomes zero.

In accordance with the foregoing, therefore, the resistances R and R are not essential to the operation of the relay according to the invention, they are each independently provided, and FIGURE 2 in which they are illustrated is a variant of the invention which permits of satisfying certain particular requirements.

If the utilisation or load current is introduced into the feedback winding by removing the connection NQ and establishing the connections MN and PQ, the output current is represented, for N l =0, as il ustrated in FIG- URE 7, by the intersection of the straight line D with the curve G i.e. the point A The slope of the line D is defined by the ratio of the number of ampere-turns of the feedback Winding a to the number of ampere-turns of the control windings b and c. The characteristic operating point when N l is different from zero is given by the intersection of the curve 6,; with a straight line derived from the line D by a translation parallel to the axis of the abscissae and algebraically equal to N l It will thus be seen that with N 1 (N IJ the straight line D intersects the curve G at B and A that with N I =(NJ the straight line D intersects the curve G at B and A and that with N I (N I or (N l there is only one possible point of intersection.

The curve G of FIGURE 8 is the characteristic curve proper of the relay according to the invention which, to sum up, supplies with N I (N Z a zero output current, and with (N I N I (N i h a zero current or a current of constant strength I depending upon whether N l has reached its value through increasing or decreasing values.

The point B corresponding to the value (N IQ and the point B corresponding to the value (N IJ are called respectively the rising or operating point and the falling or inoperative point.

Instead of a p-n-p-transistor, it is also possible to use an n-p-n-transistor provided that the polarities of the current sources U and U and the direction of the rectifier R are reversed.

I claim:

1. Magnetostatic relay comprising a magnetic amplifier having output terminals and at least one saturable magnetic core carrying at least one power winding fed with alternating current and one control winding fed with direct current, a rectifier connected in series with the power winding, a transistor having an emitter, a base and a collector, an external base-emitter circuit operatively connecting said base with said emitter and including a resistance and a first voltage source, said base-emitter circuit being grounded at a point thereof operatively connecting one side of said resistance to a corresponding side of said first voltage source, one of the terminals of the alternating-current source feeding the magnetic amplifier being grounded and the other terminal thereof being connected to the series circuit including said power winding and said rectifier, the output terminals of said magnetic amplifier being effectively constituted by the two sides of said resistance by connecting said series circuit to a point of said external base-emitter circuit operatively connecting the other side of said resistance to said base, the emitter of the transistor being connected to said first constant-voltage source, the variation of the strength of the output current of the magnetic amplifier having the effect of varying the potential of the base and thus rendering the transistor selectively non-conductive or conductive, and the utilisation circuit of the said transistor comprising a load impedance connected on the one hand to the collector of the transistor and on the other hand to a second constant-voltage source.

2. Magnetostatic relay according to claim 1, wherein for a p-n-p-transistor the power Winding of the magnetic amplifier is connected on the one hand to the alternatingcurrent feed source and on the other hand to the base of the transistor through the rectifier oriented in a direction such as to allow only the negative half-cycles to pass, the emitter of the transistor being connected to the negative pole of the first constant-voltage source and the load impedance being connected to the negative pole of the second constant-voltage source.

3. Magnetostatic relay according to claim 1, wherein a resistance is effectively connected between the rectifier and the base of the transistor.

4. Magnetostatic relay according to claim 1, wherein the collector of the transistor is connected to earth through a filtering condenser.

5. Magnetostatic relay according to claim 4, wherein a protective resistance is inserted between the collector of the transistor and the point which is connected to the filtering condenser.

6. Magnetostatic relay according to claim 5, wherein the utilisation circuit consists of a load resistance in series with the protective resistance, which is connected to the collector of the transistor, the filtering condenser having one of its electrodes connected to a point of the circuit which is situated between the two last-mentioned resistances and the other electrode being connected to ground, in such manner that the charging or discharge current of the condenser, limited by the protective resistance, is not harmful to the transistor.

7. Magnetostatic relay according to claim 1, wherein the utilisation circuit comprises a feedback winding disposed on the magnetic core of the magnetic amplifier and inserted between the collector of the transistor and the load impedance.

8. A magnetostatic relay comprising a magnetic amplifier having at least one saturabie magnetic core carrying at least one power Winding and one control winding, means for connecting said power winding for energization from an alternating current source and including a rectifier in series with said power winding, the series circuit comprising said power Winding and said rectifier having an output terminal, a transistor having base, emitter and collector electrodes, an external base-emitter circuit electrically connecting said base to said emitter and including a first voltage source and means connecting one side of said first voltage source to said emitter, means connecting said output terminal to said external base-emitter circuit for effectively producing the output of said magnetic aniplifier in said external base-emitter circuit in the part thereof between the base and the other side of said first voltage source, a load circuit connected to said collector electrode and including in series a load impedance and a second constant-voltage source of direct current, the voltage of said first and second constant-voltage source being such that the current in the load impedance is varied by predetermined changes in the potential at said output terminal which in turn is responsive to the change in energization of said control winding from a direct current source.

References Cited in the file of this patent UNITED STATES PATENTS 2,902,609 Ostrofi of al Sept. 1, 1959 2,909,674 Moore Oct. 20, 1959 2,920,213 Elias Ian. 5, 1960 2,946,896 Alizon July 26, 1960 

1. MAGNETOSTATIC RELAY COMPRISING A MAGNETIC AMPLIFIER HAVING OUTPUT TERMINALS AND AT LEAST ONE SATURABLE MAGNETIC CORE CARRYING AT LEAST ONE POWER WINDING FED WITH ALTERNATING CURRENT AND ONE CONTROL WINDING FED WITH DIRECT CURRENT, A RECTIFIER CONNECTED IN SERIES WITH THE POWER WINDING, A TRANSISTOR HAVING AN EMITTER, A BASE AND A COLLECTOR, AN EXTERNAL BASE-EMITTER CIRCUIT OPERATIVELY CONNECTING SAID BASE WITH SAID EMITTER AND INCLUDING A RESISTANCE AND A FIRST VOLTAGE SOURCE, SAID BASE-EMITTER CIRCUIT BEING GROUNDED AT A POINT THEREOF OPERATIVELY CONNECTING ONE SIDE OF SAID RESISTANCE TO A CORRESPONDING SIDE OF SAID FIRST VOLTAGE SOURCE, ONE OF THE TERMINALS OF THE ALTERNATING-CURRENT SOURCE FEEDING THE MAGNETIC AMPLIFIER BEING GROUNDED AND THE OTHER TERMINAL THEREOF BEING CONNECTED TO THE SERIES CIRCUIT INCLUDING SAID POWER WINDING AND SAID RECTIFIER, THE OUTPUT TERMINALS OF SAID MAGNETIC AMPLIFIER BEING EFFECTIVELY CONSTITUTED BY THE TWO SIDES OF SAID RESISTANCE BY CONNECTING SAID SERIES CIRCUIT TO A POINT OF SAID EXTERNAL BASE-EMITTER CIRCUIT OPERATIVELY CONNECTING THE OTHER SIDE OF SAID RESISTANCE TO SAID BASE, THE EMITTER OF THE TRANSISTOR BEING CONNECTED TO SAID FIRST CONSTANT-VOLTAGE SOURCE, THE VARIATION OF THE STRENGTH OF THE OUTPUT CURRENT OF THE MAGNETIC AMPLIFIER HAVING THE EFFECT OF VARYING THE POTENTIAL OF THE BASE AND THUS RENDERING THE TRANSISTOR SELECTIVELY NON-CONDUCTIVE OR CONDUCTIVE, AND THE UTILISATION CIRCUIT OF THE SAID TRANSISTOR COMPRISING A LOAD IMPEDANCE CONNECTED ON THE ONE HAND TO THE COLLECTOR OF THE TRANSISTOR AND ON THE OTHER HAND TO A SECOND CONSTANT-VOLTAGE SOURCE. 